949 research outputs found
Mixed d-f Block Single-Molecule Toroics
No full textSingle Molecule Toroics pp 15–66Cite as
Mixed d-f Block Single-Molecule Toroics
Keith S. Murray, Stuart K. Langley, Kuduva R. Vignesh, Gopalan Rajaraman, Kieran Hymas & Alessandro Soncini
Chapter
First Online: 24 November 2022
3 Accesses
Abstract
In this chapter, we focus on the single-molecule toroidal (SMT) behaviour of a family of “double dysprosium triangle” heptanuclear species which contain a bridging d-block M(III) or a p-block M(III) ion. They are of general formula [MIIIDyIII 6(OH)8(o-tol)12(NO3)(MeOH)5]∙3MeOH, labelled MDy 6, where o-tol = o-toluate. The parent compound has M = Cr, with subsequent family members having M = Mn, Fe, Co and Al, the latter two having diamagnetic M(III) centres. This heptanuclear family could also be made using chloride as counter-anion rather than nitrate, the molecular structures being similar to the nitrates though the unit cells are different. The LnIII ion could also be varied to include Tb, Ho and Er and, thus, allow exploration of SMT behaviour in non-Dy analogues. The syntheses, structures and magnetic and EPR properties are described, starting with the parent CrDy 6. Theoretical calculations are described in detail, with MOLCAS methods employed to determine anisotropy directions, blocking barriers and relaxation effects and a newly developed model used to calculate magnetically coupled toroidal states and the role of these states in spin dynamics. The direct simulation of the micro-Squid magnetic hysteresis loops of all family members is described as well as that of the original Dy 3 material. Toroido-structural correlations are presented with strategies developed to optimize the important ferrotoroidic coupling between Dy3 triangles in these heptanuclear toroidal species. Finally, we give a brief summary of SMT behaviour in ring-shaped 3d-4f toroidal species
2010 Seventh International Conference on Information Technology: New Generations
No full textIsaac Macwan (with Hassan Bajwa, Vignesh Veerapandian, and Xinghao Chen) is a contributing author, VHDL Implementation of High-Performance and Dynamically Configures Multi-port Cache Memory, pp. 1212-1216.https://digitalcommons.fairfield.edu/engineering-books/1057/thumbnail.jp
Empowering end-use consumers of electricity to aggregate for demand-side participation
No full textEnd-use consumers (peers) are being empowered to aggregate for direct demand-side participation through load scheduling and energy sharing. This is the result of the growth of Internet of Things (IoT) enabled loads, availability of advanced metering infrastructure, and the move towards real-time (RT) pricing of electricity. Peer-to-peer (P2P) cooperation has received significant interest in recent years, though the focus of this growing body of research is on modeling prosumer behavior in microgrids. Hence, there is a need for new methodologies to examine empowerment of all end-use consumers (not limited to prosumers) to form aggregations and develop fair rules of cooperation to reduce cost. This paper offers an optimization based methodology to address the above need for power systems. It minimizes the total cost and considers fairness using a Nash bargaining approach. Since cost and fairness are often in conflict, trade-off strategies are also presented. The model to asses fairness is nonlinear. Hence, it is transformed into a second order cone program (SOCP) and solved using GUROBI software version 7.5.2. The methodology is implemented on a sample 5-bus network, built using price and demand data from one of the load zones of Pennsylvania, New Jersey, and Maryland (PJM) power network in the United States. It is shown that two aggregations of peers participating in the sample network can reduce their total cost by 14.17% and 22.7%, while maintaining fairness. Concluding remarks highlight some of the limitations of the methodology.
A Data-Driven Methodology for Dynamic Pricing and Demand Response in Electric Power Networks
No full textThe practice of disclosing price of electricity before consumption (dynamic pricing) is essential to promote aggregator-based demand response in smart and connected communities. However, both practitioners and researchers have expressed fear that wild fluctuations in demand response resulting from dynamic pricing may adversely affect the stability of both the network and the market. This paper presents a comprehensive methodology guided by a data-driven learning model to develop stable and coordinated strategies for both dynamic pricing as well as demand response. The methodology is designed to learn offline without interfering with network operations. Application of the methodology is demonstrated using simulation results from a sample 5-bus PJM network. Results show that it is possible to arrive at stable dynamic pricing and demand response strategies that can reduce cost to the consumers as well as improve network load balance
Ferrotoroidic ground state in a heterometallic {CrIIIDyIII6} complex displaying slow magnetic relaxation
No full textToroidal quantum states are most promising for building quantum computing and information storage devices, as they are insensitive to homogeneous magnetic fields, but interact with charge and spin currents, allowing this moment to be manipulated purely by electrical means. Coupling molecular toroids into larger toroidal moments via ferrotoroidic interactions can be pivotal not only to enhance ground state toroidicity, but also to develop materials displaying ferrotoroidic ordered phases, which sustain linear magneto-electric coupling and multiferroic behavior. However, engineering ferrotoroidic coupling is known to be a challenging task. Here we have isolated a {CrIIIDyIII6} complex that exhibits the much sought-after ferrotoroidic ground state with an enhanced toroidal moment, solely arising from intramolecular dipolar interactions. Moreover, a theoretical analysis of the observed sub-Kelvin zero-field hysteretic spin dynamics of {CrIIIDyIII6} reveals the pivotal role played by ferrotoroidic states in slowing down the magnetic relaxation, in spite of large calculated single-ion quantum tunneling rates
Blockchain Social Theory and Societal Impact
No full textWe face a daily reality such that very interesting outlook changes are testing the fundamental organizations that trust is based on. The absence of trust related with information administration, which is frequently knowledgeable about the type of information breaks or essentially an adaptation of our information without our consent as well as impetus to take part in this arising decentralization of designs, is basically difficult centralization as states, monetary establishments, ventures, and associations. We perceive this trust gap posing a threat to the very institutions on which we have relied, such as financial institutions, private businesses, and government agencies. As people keep on advancing into more decentralized and self- administering (or semi-independent) associations, a new “common agreement” is fundamental. Although there has been significant discussion regarding blockchain applications and prospective results in the FinTech industry, little has been done to examine how client-driven blockchain advancements can enable a variety of purposes outside of banking. This article plans to add to that assortment of information by inspecting blockchain innovation’s likely applications, as well as its restrictions, in regions where social effect crosses, like basic liberties. This likewise examines whether blockchain innovation and its center functional standards - like decentralization, straightforwardness, equity, and responsibility - can assist with restricting unnecessary internet-based observation, oversight, and common liberties infringement that are worked with by the developing dependence on a couple of elements to control admittance to data on the web. With regards to the expected effect of blockchain innovation on society, what is conceivable and what ought to be kept away from. With the proviso that an administration instrument should be indicated, we will see further improvement in computerized power. The data introduced in this position paper upholds the possibility that blockchain and individual tokenization could make another common agreement
On the computation of probabilities and eigenvalues for random and non-random matrices
No full textThesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from PDF version of thesis.Includes bibliographical references (p. 43-44).Can you imagine doing hundreds of millions of operations on non-integers and not obtaining a single round-off error? For n < 12, the algorithm used in this thesis does exactly that. We took advantage of a floating point property that we have not seen used before. If only we had quad precision we could have gone even further and extended the algorithm without round-off error for higher values of 'n'. The problem in question concerns whether the eigenvalues are real or complex. The eigenvalues of an n-by-n real random matrix whose elements are independent random variables with standard normal are examined. An exact expression to determine the probability Pn,k that exactly k eigenvalues are real are derived in [1]. This expression was used to compute the probabilities Pn,k, but the computation was achieved only up to n = 9. For higher values of n, the symbolic expressions generated during the course of an algorithm to compute an exact probability as expressed in Mathematica code requires large amounts of memory. In this thesis, we target development of a more efficient algorithm. The symbolic algorithm implemented in Mathematica is converted into an equivalent numerical version and is implemented using MATLAB. After implementing the serial code in MATLAB, the code is parallelized using a client-server parallel computing platform named Star-p. This modified code implementation along with superior hardware in terms of better processor speeds and larger memory, has enabled the probability evaluation for all values of k up to n= 11, and for certain k values for n = 12 and 13.(cont.) An expression for the expected number of real eigenvalues En=o kpn,k is obtained in paper [2]. Results relating the rational and irrational parts of the summations n =o kpn,ki, En k=0 (Pk n,k and En= - n,k 0 k)Pn,k are conjectured. Three eigenvalue algorithms, the block Davidson, the block KrylovSchur and the Locally optimal Block Pre-conditioned Conjugate Gradient Method (LOBPCG) are analyzed and their performance on different types of matrices are studied. The performance of the algorithms as a function of the parameters , block size, number of blocks and the type of preconditioner is also examined in this thesis. The block Krylov Schur Algorithm for the matrices which are used for the experiments have proved to much superior to the others in terms of computation time. Also its been more efficient in finding eigenvalues for matrices representing grids with Neumann boundary conditions which have at least one zero eigenvalue. There exists one optimal combination of block size and number of blocks at which the time for eigenvalue computation is minimum. These parameters have different effects for different cases. The block Davidson algorithm has also been incorporated with the locking mechanism and this implementation is found to be much superior to its counterpart without the locking mechanism for matrices which have at least one zero eigenvalue.by Vignesh Peruvamba Sundaresh.S.M
How the planning, engineering and politics of transportation established, preserves and perpetuates the automobile city
No full textThesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning; and, (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis. Page [167] blank.Includes bibliographical references (p. 161-166).The last eight decades of urban transportation planning and engineering in the United States have been dominated by the hegemony of the automobile. Auto-oriented planning of the transportation and land use system has had a profound impact on the built environment both in greenfield developments and neighborhoods that predated the auto. The pedestrian quality of cities has been eroded by the automobile, and urban renewal in the United States erased many neighborhoods strongly oriented around walking and transit use. Equally pervasive as the auto itself is the place for the car in the institutional cultures and practices involved in shaping the city. The shortcomings of mobility-oriented transportation planning have been well critiqued, even from the very early days of Interstate building. In recent decades there has been a flurry of interest in articulating sustainable transportation policies to provide multi-modal accessibility and to consider the interactions between transportation, land use, and other policy realms such as health, energy, environment and equity. The current impending crisis of aging and ailing highway structures in the United States presents a momentous opportunity to reassess the need and purpose of such infrastructure, and to rebuild, reconceptualize, or remove it in a matter more consistent with current policy goals and planning processes - rather than the ones in place when initially built. Despite the interest, need and opportunity to reconceptualize aging infrastructure in America to support a more sustainable reshaping of land use and activity patterns, the potential to do so is heavily impaired by a transportation planning process that is still dominated by the tools, methods and assumptions, political biases, procedural failures, and instilled human behaviors of the first highway-building era. The McGrath Highway in Somerville, MA is used as a case study to discuss how persistence of 1950s technical, procedural and political dysfunctions threaten to undermine this opportunity. Short-term actions and strategies to avoid this impending fate are suggested for McGrath Highway with applicability to a wider national context of similar opportunities.by Vignesh Krishnamurthy.S.M.in TransportationM.C.P
Discriminating ferrotoroidic from antiferrotoroidic ground states using a 3d quantum spin sensor
No full textMolecular toroidal states have come to the forefront as candidates for next-generation quantum information devices owing to their bistability and protection from weak, short-range magnetic interactions. The protection offered by these non-magnetic vortex spin states proves to be a double-edged sword as inferring their existence in a molecular system has yet to be achieved through experimental means alone. Here, we investigate the anomalous, sickle-shaped, single-crystal magnetisation profile arising in μ-SQUID measurements of a novel CrDy3 molecule. Theoretical modelling supported by ab initio calculations demonstrates that the weak field CrDy3 spin dynamics is resultant from quantum superposition of the CrIII spin states determined by three competing interactions: (i) the alignment of the CrIII magnetic moment to the external magnetic field, (ii) the zero-field splitting of the CrIII ground quartet, and (iii) coupling to the remnant magnetisation of the toroidal ground state in the Dy3 triangle. If zero-field splitting of the central transition metal ion is quenched, it operates as a quantum spin sensor, which can be exploited to experimentally discriminate between ferrotoroidic and antiferrotoroidic ground states in MDy6 double triangle complexes through electron paramagnetic resonance experiments and single-crystal magnetisation measurements with a restricted field sweeping domain
Transgenerational response to early spring warming in Daphnia
No full textTemperature and photoperiod regulate key fitness traits in plants and animals. However, with temperature increase due to global warming, temperature cue thresholds are experienced at shorter photoperiods, disrupting the optimal seasonal timing of physiological, developmental and reproductive events in many species. Understanding the mechanisms of adaptation to the asynchrony between temperature and photoperiod is key to inform our understanding of how species will respond to global warming. Here, we studied the transgenerational mechanisms of responses of the cyclical parthenogen Daphnia magna to different photoperiod lengths co-occurring with warm temperature thereby assessing the impact of earlier spring warming on its fitness. Daphnia uses temperature and photoperiod cues to time dormancy, and to switch between sexual and asexual reproduction. Daphnia life cycle offers the opportunity to measure the relative contribution of plastic and genetic responses to environmental change across generations and over evolutionary time. We use transgenerational common garden experiments on three populations ‘resurrected’ from a biological archive experiencing temperature increase over five decades. Our results suggest that response to early spring warming evolved underpinned by a complex interaction between plastic and genetic mechanisms while a positive maternal contribution at matching environments between parental and offspring generation was also observed.<br/
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